The day following our advance I was promoted to the rank of corporal, on the recommendation of Captain Buel, my appointment to date from the fifteenth. On the sixteenth our lines were advanced to Vienna, a station on the Leesburg Railroad, and on the seventeenth as far as Fairfax Court House, the Confederates falling back toward Centreville and Manassas without offering the least resistance. FORAGING AND SCOUTING. We are spending our time mostly in foraging, scouting, and patrolling. In consequence of imperfect transportation, the cavalry especially is compelled to seek its own forage, with which, however, the country abounds. Corn is found in "right smart heaps," as the natives say, either in the fields or barns, and hayricks dot the country on every side. But there is a certain degree of scrupulousness on the part of some of our commanders with regard to appropriating the produce of the "sacred soil" to our own use, which greatly embarrasses our foraging expeditions, and exasperates not a little those of us who are needy of the things we are at times ordered not to take. It is no uncommon thing to find one of our men stationed as safeguard over the property of a most bitter Rebel--property which, in our judgment, ought to be confiscated to the use of the Union, or utterly destroyed. We do not believe in handling Rebels with kid gloves, and especially when we know that the very men whom we protect are constantly giving information to the enemy of all our movements, and using their property whenever they can to aid and comfort the cause of treason. We are too forcibly reminded of the fable we used to read in our schoolboy days, of the Farmer and the Viper. We are only warming into new life and strength this virus of Rebellion, to have it recoil upon ourselves. We hope our authorities will soon discover their error, and change their tactics. Our scouting is on a limited scale, though it affords considerable exercise and excitement. Thereby we are learning the topography of the country, and making small maps of the same. We are traversing the forests, through the wood-roads and by-paths which run in every direction; strolling by the streams and ravines, and gaining all the information which can be of use to us in future manoeuvrings. We scout in small squads over the entire area occupied by our forces, and often beyond; and, now and then, more frequently in the night, we patrol between our picket posts, to ascertain that all is well at the points most exposed to danger. The principal object of scouting is to learn the strength and position of the enemy, while the object of patrolling is to learn our own.